The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Norepinephrine is often used during CPR (cardio-pulmonary resuscitation), and in the treatment of cardiac arrest and profound hypotension. Norepinephrine is also used for blood pressure control in certain acute hypotensive states, including for example sympathectomy, poliomyelitis, pheochromocytomectomy, spinal anesthesia, myocardial infarction, blood transfusion, and septicemia.
Currently, norepinephrine is marketed as Levophed®, which is a concentrated 4 mg per 4 mL norepinephrine bitartrate formulation to be administered by intravenous infusion following dilution with dextrose or dextrose and sodium chloride injection. Norepinephrine is also marketed by Baxter which supplies as a norepinephrine concentrate that is free of sodium metabisulfite and packaged under nitrogen. Unfortunately, most, if not all diluted commercially available norepinephrine formulations lack storage and should therefore be discarded within one day after reconstitution when stored at room temperature. Consequently, risk for microbial contamination and dilution errors is present. In addition, Levophed also contains sodium metabisulphite as an antioxidant, and carries a warning label that sulfite may cause allergic type reactions including anaphylactic shock and life threating or less severe asthmatic episodes in susceptible people. Table 1 depicts ingredients of currently marketed norepinephrine compositions.
TABLE 1Composition of currently marketed Norepinephrine Bitartrate Products.NorepinephrineLevophed ®BitartarateIngredient(Hospira)(Baxter)Norepinephrine Bitartrate  1 mg/mL1 mg/mLequivalent toNorepinephrine BaseSodium ChlorideIsotonicIsotonicSodium Metabisulphite0.2 mg/mL—pH3-4.53-4.5Water for injectionq.s. 1 mLq.s 1 mL
Stability of Levophed® and Norepinephrine bitartrate injection (Baxter), in normal saline solutions is presented in Table 2 and Table 3 where norepinephrine was diluted to a concentration of 16 μg/ml. Stability was assessed in 250 ml saline at accelerated (i.e., 40±2° C. and 75±5% relative humidity, duration as indicated) and long term stability (i.e., 25±2° C. and 60±5% relative humidity, duration as indicated) storage conditions.
TABLE 2Stability study of Levophed ® diluted in 0.9% Saline (Hospira) at 16 μg/mL.Storage Condition25 ± 2° C./60 ± 5% RH40 ± 2° C./75 ± 5% RHTime PointInitial1 Month2 Month3 MonthInitial1 Month2 Month3 MonthAssay97.398.997.991.998.896.580.271.9Total0.05—0.718.080.031.965.299.73Impurities
TABLE 3Stability study of Norepinephrine bitartrate injection [Baxter] diluted in 0.9% Saline(Hospira) at 16 μg/mLStorage Condition25 ± 2° C./60 ± 5% RH40 ± 2° C./75 ± 5% RHTime PointInitial1 Month2 Month3 MonthInitial1 Month2 Month3 MonthAssay99.999.797.092.299.491.582.977.6Total0.081.732.6810.170.102.344.466.71Impurities
As can be seen from the results, the norepinephrine at ready-to-inject concentrations underwent significant degradation. Oxidative degradation could possibly be reduced or even prevented by addition of effective amounts of sodium metabisulphite to the ready-to-inject norepinephrine solution. However, the quantities of sodium metabisulphite that would be administered by injection of 250 ml of the ready-to-inject solution would be substantial and detrimental to the patient. To avoid issues associated with sodium metabisulphite, efforts have been made to provide norepinephrine formulations with a non-sulfite anti-oxidant. For example US 2016/0058715 teaches a ready-to-inject dosage form of norepinephrine that uses butylated hydroxyl anisole as an anti-oxidant. While generally deemed safe for topical and cosmetic use, butylated hydroxyl anisole was shown to produce some renal and hepatic damage (e.g., Int J Toxicol. 2002; 21 Suppl 2:19-94).
In other attempts to provide ready-to-administer norepinephrine formulations with increased storage stability and reduced risk of human error, the pH on the injectable solution was reduced to between 3.2 and 3.6 with 40-200 μg/ml norepinephrine as is described in WO 2015/128418. While such formulations exhibited reduced degradation as compared to higher pH formulations, significant discomfort can occur at the injection site. Worse yet, at the pH used, norepinephrine isomerized relatively quickly from the active R (−) isomer to the inactive S (+) isomer. Isomerization is also encountered at exposure of norepinephrine to higher temperatures.
Therefore, there is a need for improved stable, low concentration, ready-to-inject and antioxidant free norepinephrine formulations, and methods of manufacturing and storing the same.